Conventionally, there is only one host that controls resources. For example, in an SD™ memory card in a digital camera, only the digital camera controls a file in the SD memory card.
However, recently, an SD memory card with a wireless LAN function has appeared. In such a memory card, two hosts of the digital camera and wireless LAN function are present in the SD memory unit. If the two hosts simultaneously access the file of the SD memory unit, a file management table is simultaneously changed and the file may be destroyed.
Therefore, in order to prevent a plurality of hosts from simultaneously accessing the SD memory unit, an exclusive control operation is performed according to an OS of the digital camera. As a result, the host that accesses the SD memory unit is limited to one of the hosts.
However, with the above configuration, the file can be prevented from being destroyed, but the usability of the SD memory card is extremely degraded.